"We knew that people value the loss of consumer choice but we had never measured it," says Parkinson.

She says being able to put a value on loss of choice means it can be included in cost benefit analyses for different programs, resulting in more appropriate policy decisions.

Anything that involves banning, or making compulsory, certain behaviours or products is a mandatory health program, says Parkinson.

From water fluoridation to compulsory bicycle helmets or banning smoking in public places, every public health program carries with it costs as well as benefits.

Policy makers often weigh these up in dollar terms when deciding whether to go ahead with a program.

Financial costs of the intervention and any adverse effects must be weighed against the benefits including improvements in public health.

But, says Parkinson, the loss of individual choice that comes with mandatory health programs is often not formally included in this trade-off, because there has been no way to measure it.

Choice experiments

Parkinson and colleagues have now developed a method that can put a dollar value on this loss of choice, using what are known as discrete choice experiments.

These are surveys of the kind that businesses use all the time to study consumer preferences for anything from cars to telephone plans.

"It's a standard econometric process used worldwide, but the application is quite unique," says Parkinson.

She and colleagues surveyed 535 participants online about one of three health programs, which differed in various respects: folate fortification of bread flour, the banning of trans-fats and influenza vaccination of children.

The vaccination program was an active intervention and the benefits were more for society as a whole, than to the individual, says Parkinson.

However, the banning of unhealthy trans-fats in food products was of benefit to individuals, without them having to do anything themselves.

"The other thing is that there are no real adverse events from banning trans-fats but there can be for influenza vaccine, even though they are very rare," says Parkinson.

Each participant was presented with eight different scenarios involving their allocated health program and asked to choose which one they preferred.

Following a series of complex calculations, Parkinson and colleagues worked out that the loss of consumer choice for the vaccination program was worth $112 per person.

For the folate fortification program the figure was just over $18 and for the trans-fat program it was effectively zero.

"We found that people really value their loss of consumer choice with regards to the influenza vaccine," says Parkinson.

"With the trans-fat program, people didn't care that it was mandatory because it meant they were never going to be exposed to trans-fat."

Parkinson emphasises that this was a relatively small pilot study and the absolute dollar values are of limited significance.

But she says the findings support the use of the method to measure the loss of consumer choice, and she is confident in the findings that loss of choice bothers people more in some cases than others.

Parkinson believes the study sheds light on the reason why vaccination is so controversial.

"I think that controversy partially stems from the fact that people value their loss of consumer choice a lot more," she says.